Residual error

PKPDsim can simulate residual errors on top of your observed data, which
can be done with the res_var argument to the sim() function.
This argument requires a list() with one or more of the
following components:

prop: proportional error:

add: additive error:

exp: exponential error:

These list elements can be combined, e.g. for a combined proportional and additive
error model one would write e.g.: res_var = list(prop = 0.1, add = 1), which
would give a 10% proportional error plus an additive error of 1 concentration unit.